Data storage cartridges have been used to house removable data storage media. FIGS. 1A-1B show one type of data storage cartridge 100 comprising a housing 102 containing a magneto-optical (MO) disk medium 104. The configuration and design of this MO cartridge 100 conforms to standards set by the ECMA Technical Committee TC31, which provides a uniform standard that can be followed by MO cartridge and MO drive manufacturers. This standard was published by ECMA as “Standard ECMA-322, Data Interchange on 130 mm Magneto-Optical Disk Cartridges—Capacity: 9,1 Gbytes per Cartridge” (June 2001), which is incorporated by reference herein in its entirety as if fully set forth below.
The housing 102 serves as a protective enclosure for the disk medium 104 and includes access windows 106 covered by a sliding shutter 108. A detent 110 is provided in the shutter 108 to enable a loading mechanism in a data drive to engage and slide the shutter 108. When the MO cartridge 100 is inserted into an MO drive in the loading direction L, a shutter opening mechanism in the MO drive engages the detent 110 to open the shutter 108 and uncover the windows 106, thereby exposing a portion of the MO disk 104. The MO disk 104 may consist of two sides assembled together with their recording layers on the inside. Data can be written onto both sides of the disk 104 as marks in the form of magnetic domains in the recording layer and can be erased from the disk 104 with a focused optical beam, using a thermo-magnetic effect. The data can be read with a focused optical beam, using the magneto-optical effect.
Another type of data storage system is known as holographic storage, described in detail in U.S. Pat. No. 5,719,691, entitled, “Phase Correlation Multiplex Holography,” to Curtis et al., issued Feb. 17, 1998, and U.S. Pat. No. 6,191,875, entitled, “Process for Holography Using Reference Beam Having Correlated Phase Content,” to Curtis et al., issued Feb. 20, 2001, incorporated by reference herein in their entireties. Holographic data storage systems store information or data based on the concept of a signal beam interfering with a reference beam at a holographic storage medium. The interference of the signal beam and the reference beam creates a holographic representation, i.e., a hologram, of data elements as a pattern of varying refractive index and/or absorption imprinted in a volume of a storage or recording medium such as a photopolymer or photorefractive crystal.
In holographic data storage (HDS), light from a coherent laser source is split into two beams, signal (data-carrying) and reference beams. Digital data to be stored are “encoded” onto the signal beam via a spatial light modulator (SLM). The data are arranged into data pages or large arrays, and these data pages are translated into pixels of the spatial light modulator that either block or transmit light. The light of the signal beam traverses through the modulator and is therefore encoded with the “checkerboard” pattern of the data page. This encoded beam then interferes with the reference beam through the volume of a photosensitive recording medium, storing the digital data pages. The interference pattern induces modulations in the refractive index of the recording material yielding diffractive volume gratings. The reference beam is used during readout to diffract off of the recorded gratings, reconstructing the stored array of bits. The reconstructed array is projected onto a pixelated detector, such as a CMOS photo-detector array or the like. The detector reads the data in parallel, and the data can then be decoded into the original encoded data.
It may be desirable that the holographic data storage medium be provided in disk form and housed in a cartridge housing similar to the housings 102 for MO cartridges 100. This enables HDS manufacturers to utilize existing MO cartridge designs and handling mechanisms for easy conversion to HDS applications. However, the HDS medium functions differently from the MO storage medium, and therefore has different handling considerations. In particular, the HDS medium is sensitive to light and can be damaged if exposed to the read/write mechanism of an MO drive, or even ambient light. If an HDS medium is provided in a cartridge similar to the cartridge design of another media type, it would be desirable to implement protection mechanisms to prevent or inhibit attempts to load and read data from the HDS media using another type of non-HDS media drive. In addition, the data transfer mechanism used with certain storage media types, such as, for example, HDS media, may be structurally different from the data transfer mechanisms of other media types and may therefore have different design considerations.
Accordingly, there is a need for an improved design for a removable data storage cartridge housing a data storage medium.